For attaching a lid portion of a potentiometer or for connecting several potentiometers, it is known to provide rims at the elements which have to be connected along the contact surfaces such that a bead is formed after assembling. A strap retainer having a u-shaped cross section is placed around this bead and is tightened by a kind of clip.
In a potentiometer with several potentiometer decks it is necessary to align the potentiometer resistors with sliders arranged on a common potentiometer shaft, such that, with a determined position of the potentiometer shaft, the output zero, e.g., results simultaneously from all potentiometers. The potentiometer resistors are located in shallow, annular housing parts which are placed one on top of the other and are rotated relative to each other for adjustment. The potentiometer shaft with all sliders extends through all the housing parts. Then the housing parts are tightened by the strap retainers in their adjusted positions.
With this kind of connection the radially projecting clips are inconvenient. Also tightening of the strap retainers is labor-intensive. It has to be made with great care, in order to avoid malajustment during the tightening process. Besides the strap retainers with clips are relatively expensive.
"Heat-shrinkable sheaths" are known. They consist of a material which permanently shrinks very much when they are heated. Such heat-shrinkable sheahs are for example used to protect soldering joints: A piece of heat-shrinkable sheath is pushed over a soldering joint and is heated. It shrinks and thus adapts to the shape of the enclosed elements. In this way the soldering joint is covered waterproof and relieved from tension. Materials of this kind are described in U.S. Pat. No. 2,027,962 and U.S. Pat. No. 3,086,242.
It is also known to connect elements by means of a material which permanently shrinks very much when it is heated.
From DE-A-No. 2 527 838 a tube connection, particularly for pressurized air conduits, or suction conduits is known which is established by a heat-shrinkable sheath extending around the adjacent tube ends. DE-B-No. 1 024 838 shows a tube connection for drain tubes in which a bushing bridging the tube ends consists of a plastic material which, after application to the tube end to be enclosed, shrinks upon the supply of heat.
In the known tube connections the heat-shrinkable sheath section is supported by the external surface of the tube ends. In some embodiments a flange projecting outwardly or a bead is provided on each tube end the heat-shrikable sheath extends around the flanges or beads. The connection is either frictional in axial direction or has flanges or the like projecting outwardly beyod the tube surface. Besides the angular position of the tube ends relative to the tube axis is non-critical in tube connections unlike in housing parts of potentiometers.
From U.S. Pat. No. 3,513,429 heat responding actuators are known which have a longitudinally tensioned element which is shrinkable by heat and which receives two contact elements. Under the influence of heat this shrinkable element changes its length and thereby causes the contact elements to be moved towards each other. The heat-shrinkable element can also be rotated in circumferential direction such that it causes relative rotational movement of the contact elements under the influence of heat.